Chemical warfare has existed for millennia. As far back as 1000 BC,
the Chinese used arsenical smoke as a weapon.1 In
the last century, chemical agents have been used in warfare on numerous occasions,
from World War I to the Iran-Iraq conflict.2 The
world remains vulnerable to the deliberate use of chemical agents as weapons
of mass destruction. Chemical attacks can be delivered with almost any type
of conventional ballistic weapon, spray device, or by nontraditional means,
such as that used by the Aum Shinrikyo religious cult to launch 2 attacks
in public places in Japan by using sarin gas. The first attack occurred in
Matsumoto, Japan, in June 1994.3 The second
attack occurred in a Tokyo subway in March 1995.4 Terrorists
involved in this attack carried diluted sarin solution in plastic bags into
subway trains and punctured the bags with sharpened umbrella tips. This released
diluted sarin vapor into 3 convergent lines of the Tokyo subway system.5 This attack is the largest disaster caused by nerve
gas in peacetime history.4 These attacks illustrated
how an ill-prepared disaster management system can become overwhelmed.